An inkjet method which supplies a functional liquid containing a conductive material to a predetermined position on a substrate by a required amount is known (see Patent Documents 1 and 2, for example) as a related art method of forming a wiring pattern used in an electronic circuit, etc. The inkjet method has advantages that, compared to a photolithography method using an exposing apparatus, expensive apparatuses or facilities are not needed, the number of processes is smaller, and an efficiency of utilizing a material is higher. In particular, when a multi-layer wiring substrate having multiple wiring layers and an electronic element using the same are manufactured, it is necessary to electrically connect upper and lower wiring layers through a contact hole formed in an insulating layer which separates upper and lower wiring layers. The inkjet method may be applied to filling in such a contact hole or to the process of forming upper and lower wirings.
For example, in a method disclosed in Patent Document 1, a lyophobic area is formed on a region for forming a contact hole on a lower layer wiring in advance and then applying an insulating layer forming material to form a contact hole, the lyophobic area is removed by irradiating light, and then a second wiring is formed by an applying method.
Moreover, in a method disclosed in Patent Document 2, a surface modifying layer which is made of a hydrophobic material is patterned on an insulating layer, and a solution which can dissolve the insulating layer is applied by inkjet to dissolve a part of the insulating layer that is not covered with the surface modifying layer to form a contact hole and further fill the contact hole with the applying method.
However, with the above-described method disclosed in Patent Document 1, there is a problem that, while a diameter of the contact hole may be adjusted by changing an ejecting amount of lyophobic liquid droplets in the process of forming the lyophobic area, an applying method is used, so that there is a lower limit to a size of the contact hole. For example, with the inkjet method, control of not more than 1 pl (pico liter) of liquid droplets is difficult and further a functional solution for forming the lyophobic area undergoes wet spreading on the substrate. Moreover, when multiple nozzles are used, a variation in an impact position of the functional solution occurs among nozzles. Due to these reasons, it is difficult to form the contact hole of a size of less than or equal to 50 micrometers, for example. Moreover, the second wiring is also formed by the applying method, so that it is similarly difficult to accurately fill the contact hole with a conductive functional liquid, or to micro fabricate a second wiring layer.
Furthermore, with the method disclosed in the above-described Patent Document 2, the surface modifying layer which is made of the hydrophobic material is patterned on the insulating layer with a laser, etc., making it possible to form a fine contact hole which is specified with a laser beam diameter. However, there is a problem that, as the conductive material is applied on the hydrophobic material when the contact hole is filled to form an upper wiring layer, a shape of an upper wiring is disturbed, making it difficult to obtain a fine upper wiring.